Various standards for multiplex-transmitting information of each multimedia have been established, with respect to multimedia terminals for realizing services such as a videophone by transmitting media information such as video, audio or data.
With respect to multimedia terminals for realizing TV phone service provided by the W-CDMA third generation mobile phones, for example, the ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) Recommendation, H.324 (Terminal for low bit-rate multimedia communication) is applied as one of the standards for multiplex-transmitting multimedia information. In a multimedia terminal in conformity with the international recommendation, the ITU-T Recommendation, H.324, the international recommendation, the ITU-T Recommendation, H.245 is applied as the AV communication control protocol that exchanges various setting for transmitting media information and determine, meanwhile the international recommendation, the ITU-T Recommendation, H.223 (Multiplexing protocol for low bit rate multimedia communication), is applied as a multimedia multiplexing system.
Moreover, in a multimedia terminal for realizing TV phone service used in internet communication, for example, the IETF (Internet Engineering Task Force) Standard, SIP (Session Initiation Protocol) is applied as one of the standards for multiplex-transmitting multimedia information. In a multimedia terminal in conformity with the IETF Standard, SIP, the IETF Standard, RTP (Real time Transport Protocol)/RTCP (Real time Transport Control Protocol) is applied as a multimedia-multiplex system.
In communication among multimedia terminals, it is necessary not only to establish a communication path for transmitting information, but also to establish an encoding method for media information or a transmission method for encoded media information, with respect to media information such as video or audio, etc. that is actually transmitted and received among the terminals. In the ITU-T Recommendation, H.324, multimedia communication among multimedia terminals is established through two steps including a communication procedure for establishing a communication path, referred to as “Call control procedure”, and a communication procedure for establishing the encoding method for media information of video or audio, etc. or the transmission method for the encoded media information after communication such as called “AV media control sequence has been established”. On the other hand, in the IETF Standard, SIP, multimedia communication among multimedia terminals is established by a communication procedure that concurrently establishes a communication path and an encoding method of media information such as video and audio or a transmission method for the encoded media information. That is, with respect to communication information related to video and audio, for example, encode capability of media, in the multimedia terminal in conformity with the ITU-T Recommendation, H.324, information transmission and determination are performed in the media control procedure after having established the communication path, and in the multimedia terminal in conformity with the IETF Standard, SIP, information transmission and determination are performed in the call-control and media-control procedures associated with the establishment of communication paths.
Therefore, there causes a problem in that notifying timings of terminal information related to media information are different, when mutual communication is realized among the multimedia terminals in conformity with the ITU-T Recommendation, H.324 and the multimedia terminal in conformity with the IETF Standard, SIP, which have different communication procedures. For example, there is a problem in that the multimedia terminal in conformity with the ITU-T Recommendation, H.324 can not inform the multimedia terminal in conformity with the IETF Standard, SIP, when they try to mutually communicate, because the terminal information related to media information of a calling terminal requesting communication start is not included in the communication procedure of the terminals in conformity with the ITU-T Recommendation, H.324 at the time of communication start.
Coping with the above problems, in Japanese Laid-Open Open Patent Publications 1998-334007 and 2000-285043, it is described, as an email type facsimile device, how to relay between the different communication procedures in which information is transmitted through an IP network and through a circuit exchange network. Even in communication of facsimile devices, it is necessary to inform each other of terminal information such as receivable data type or video quality selection between transmitting facsimile devices and receiving facsimile devices, and therefore the solutions to the problems are now disclosed.
In particular, the prior art described in Japanese Laid-Open Open Patent Publications 1998-334007 includes a transmitting facsimile type email device, a facsimile type email device as a relay unit, a server, and a receiving facsimile device. Their terminal information such as telephone number of the facsimile device, mail address, receivable data type or video quality selection is managed in the server. In this situation, it is pointed out that the information is automatically registered in a database of the server, if an operator inputs information items corresponding to the terminal information and transmits the input information by predetermined operation. Then, the transmitting facsimile device can obtain the terminal information in the database by inquiring the terminal information on the receiving facsimile device when facsimile transmitting, select a most suitable transmitting method, and transmit the facsimile information.
Moreover, the prior art described in Japanese Laid-Open Open Patent Publications 2000-285043 includes, in an environment composed of plural IP networks, a DNS (domain name system) server and a means for inquiring another server of terminal information to obtain the information if the terminal information is not stored in the database of the server. Therefore, even if the terminal information related to the receiving facsimile device has not been stored directly, the terminal information may possibly be obtained, for example, by inquiring a server in the IP network in which the terminal is included, and facsimile information can be transmitted in a wider-area network environment. At this moment, by automatically registering the terminal information obtained from another server into its own server, the terminal information of the receiving facsimile device can be obtained swiftly from the next time onward.
As described above, in a multimedia terminal in conformity with the ITU-T Recommendation, H.324, two steps of procedures are executed, in which a transmission path (call control procedure) and media communication (AV media control procedure) are established. On the other hand, in a multimedia terminal in conformity with the IETF Standard, SIP, the call control procedure and the AV media control procedure are executed at the same time. Therefore, when both the terminals are mutually connected, there may be a problem in that necessary information is insufficiently exchanged due to the difference of the communication procedures.
Moreover, in the method for obtaining the terminal information related to the receiving facsimile devices disclosed in above Japanese Laid-Open Open Patent Publications 1998-334007 or 2000-285043, necessary information items must be inputted by an operator in advance. In other words, the specification related to the receiving facsimile devices must be obtained. Moreover, if there is information that can not be usually recognized because the information is only exchanged by communication procedures between the devices, a problem occurs in that the present method can not be applied.
In the multimedia terminals such as those in conformity with the ITU-T Recommendation, H.324 or in conformity with the IETF Standard, SIP, in addition to information items selected by a user through an operation panel, etc., there exists terminal information that is determined by specific device specifications such as, for example, parameters related to a media encoding method or parameters related to a multiplex-transmission system for encoded media information, exchanged only by communication procedures among the terminals, and that can not be usually recognized.
Therefore, the present invention has been made accordingly in order to provide a communication service unit and an operation method for performing connection sequence, wherein information including the terminal information that the user can not obtain can be easily and automatically registered into the database, and, even in the case of communication between the multimedia terminals having communication procedures differing from each other, the user can start mutual communication without paying attention to the fact that those terminals have communication procedures differing from each other.